Visit `param_env` field in Obligation's `TypeFoldable` impl

This oversight appears to have gone unnoticed for a long time
without causing issues, but it should still be fixed.

1 files changed, 2 insertions, 1 deletions

diff --git a/compiler/rustc_infer/src/traits/structural_impls.rs b/compiler/rustc_infer/src/traits/structural_impls.rs
index c4a2ecee096..b48ca3bd0c0 100644
--- a/compiler/rustc_infer/src/traits/structural_impls.rs
+++ b/compiler/rustc_infer/src/traits/structural_impls.rs
@@ -70,6 +70,7 @@ impl<'tcx, O: TypeFoldable<'tcx>> TypeFoldable<'tcx> for traits::Obligation<'tcx
     }
 
     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
-        self.predicate.visit_with(visitor)
+        self.predicate.visit_with(visitor)?;
+        self.param_env.visit_with(visitor)
     }
 }